This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for ELECTRODE ASSEMBLY AND DYNAMIC FOCUS ELECTRON GUN UTILIZING THE SAME earlier filed in the Korean Industrial Property Office on Nov. 23, 2000, and there duly assigned Serial No. 2000-70005 by that Office.
1. Field of the Invention
The present invention relates to an electrode assembly and a dynamic focus electron gun utilizing the same, and more particularly, to an electrode assembly having first and second electrodes for forming at least one dynamic focus quadrupole lens to emit electron beams, and an electron gun utilizing the electrode assembly.
2. Description of the Related Art
The performance of a cathode ray tube (CRT) is dependent upon the state in which emitted electron beams land on a screen. Thus, in order to achieve accurate landing of the emitted electron beams on a fluorescent point of a phosphor screen, various techniques to improve focusing characteristics and reduce astigmatism of electronic lenses have been proposed.
In particular, in order to prevent electron beams landing on a phosphor screen from being elongated in an elliptic shape due to a difference in barrel and pincushion magnetic fields occurring when electron beams emitted from an electron gun are deflected by a deflection yoke, a dynamic focus electron gun by which the electron beams emitted therefrom are made relatively elliptical in synchronization with horizontal and vertical deflection periods, is used.
A quadrupole lens is described in detail in U.S. Pat. No. 4,814,670 to Suzuki et al. for Cathode Ray Tube Apparatus Having Focusing Grids with Horizontally and Vertically Oblong Through Holes and U.S. Pat. No. 5,027,043 to Chen et al. for Electron Gun System with Dynamic Convergence Control. The first and second dynamic quadrupole lenses make electron beams emitted from an electron gun be relatively elliptical in synchronization with horizontal and vertical deflection periods. Accordingly, the electron beams landing on a screen of a CRT become circular throughout the entire area of the screen.
According to the conventional dynamic focus electron gun, the magnifications of dynamic quadrupole lenses are set only by a voltage difference between a static focus voltage and a parabolic waveform signal. Thus, in order to increase an average magnification of dynamic quadrupole lenses, the average voltage of the parabolic waveform signal must be relatively high. This problem is more serious for larger CRTs. In other words, the performance, reliability and lifetime of a dynamic focus electron gun may deteriorate by application of high driving voltages.
It is therefore an object of the present invention to provide an electrode assembly which can improve the performance, reliability and lifetime of an electron gun by performing a desired dynamic focusing action even by application of relatively low voltages, and a dynamic focus electron gun utilizing the electrode assembly.
It is another object to provide an electrode assembly that is easy to manufacture.
It is still another object to provide an electrode assembly that is inexpensive to manufacture.
To achieve the above and other objects of the present invention, there is provided an electrode assembly including at least first and second electrodes for forming one or more dynamic quadrupole lenses to emit electron beams, and a dynamic focus electron gun using the same. A first parabolic waveform signal having voltages decreasing from the center to the periphery of a screen on which the electron beams land is applied to the first electrode, and a second parabolic waveform signal having voltages increasing from the center to the periphery of the screen is applied to the second electrode, in synchronization with horizontal and vertical deflection signals for horizontally and vertically deflecting electron beams emitted from the electrode assembly.
According to the electrode assembly of the present invention and the electron gun utilizing the same, a voltage applied between the first and second electrodes becomes relatively high by the interrelationship between the first and second parabolic waveform signals. Accordingly, even if the average of the first and second parabolic waveform signals is decreased, a desired dynamic focusing function can be performed, thereby improving the performance, reliability and lifetime of the electron gun.